Re: Electrolytic Capacitor Removal NO Desoldering Required


 

On Tue, Apr 21, 2020 at 10:59 PM, Brendan wrote:


I replaced the surface mount caps on my TDS420 with that method. Every twist
made my heart race. It worked. Did I like doing it? Nope. If I would have had
tweezers I would have used those for sure. You still have to wipe off the pad
with an iron to remove the left over lead that you twist off so you don't
really save the pad from any heat cycles. I also had a really hard time
getting a good thermal transfer due to the leaked electrolytic even after
trying to clean with a scratch pen.
Several years ago, I sidestepped into TDS400/500/600 land. Many in those series suffered from the leaking caps syndrome.
I must have "unscrewed" hundreds of caps and never lifted a pad. The bonding of the pads is very much stronger than it was with 70's PCBs.

I have watched some of the Mac laptop repair videos by Louis Rossman and was astonished what amount of hot rubbing and scraping the pads can endure. To think that in the 70's, normal quality copper pads could be just pushed across the epoxyglass substrate at soldering iron temperatures.

These days I own a fine Weller tweezer but I don't think I'd prefer using that. Unscrewing is effortless and quick.
I think I read someone recommend pulling while turning. I don't think that's a good idea. It defeats the idea of tearing (shearing?) the legs from/across the pad in parallel with the bond layer.
After removing the cap, the remaining solder and electrolyte residue can be removed from the pads by rubbing with a hot iron and flux, unless the pads have been damaged too much. Finish by cleaning the board. I can recommend having a look at how Louis performs his Mac repair work, it may surprise you. He's pretty rough on the boards but doesn't seem to do damage often.

Raymond

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